Heat treatment of steel rails and shapes



Patented st. 11, 1932 UNlTED JOHN BRUNNER, OF CHICAGO, ILLINOIS HEAT TREATMENT OF STEEL RAILS AND SHAPES No Drawing.

This invention relates to metallurgy and more particularly to the heat treatment of metals and alloys to improve the qualities thereof and still more particularly to the heat treatment of steel rails and shapes.

This invention is substantially an improvement of the invention set forth in my U. S. Patent No. 1,277,372 issued September 3, 1918.

The process of U. S. Patent No. 1,277,372

substantially comprises a method of heat treating steel rails and shapes to obtain therein a more uniform and fine-grain structure and a better surface than had heretofore been obtainable. The ,method substantially comprises'rolling the railto a. size larger than the desired finished size"; cooling the rail to temperatures below the thermal critical range; reheating the-rail to a temperature above the thermal critical temperature (approximately 8001C.); rolling the rail tothe desired finished size; and slowly cooling the rail to room temperature. This method produced a finished rail "having a fine grain structure which imparted thereto great toughness. The rail-product, however, did not possess sufiicient surface hardness to make it resistant to severe service conditions.

One of vtheohjects of the present invention is to increase the surface hardness of the rail product of my prior invention.

' Another object of the present invention is to' provide a heat treating method whereby the surface hardness of a steel rail shape may be materially increased.

Another object of the present invention is 'toi-provide-a steel'rail having an interior of relative high ductility and an exterior of relative high hardness.

' Another object of the present invention is to improve and facilitatethe manufacture of steel rails and shapes.-

Other objects and advantages will be apparent as the invention is more fully disclosed.

In accordance with the objects of the present invention I have found that I may impart a relatively high surface hardness to the'relatively tough fine grained rail shape prepared in accordance with the invention of my prior patent, thereby materially increasing the re- Application filed June 17,

1931. Serial No. 545,150.

sistance of the rail to service conditions by subjecting the rail to a certain heat treatlng method. The method substantially comprises the following steps At the conclusion of the final rolling operation the finished rail is cooled to temperatures approximating 300 0., and is then reheated to a uniform temperature which is slightly above the thermo-critical range of the specific composition of steel used therein and is then cooled in a quenching medium until the surface temperature thereof has been lowered at least partially through the blue-heat range (approximately 288 to 316 C.) but to temperatures not lower than 250 C., thereafter the rail shapes are reheated to a uniform temperature higher than 300 C. but below the thermal critical range (approximating 600 (3.), following Which they are slowly cooled to atmospheric temperature.

In this manner I first effect a refinement of the internal grain structure of the rail, and then a hardening of the surface portion thereof, and thereafter anneal to impart to 5 the rail the desired internal grain structure and the desired amount of external surface hardness.

As a specific embodiment of the practice of this invention I will disclose the method as applied to a steel rail composition comprising carbon.{l0-.85% manganese.4=01.60% phosphorousnot over .08%; sulphur, not over 08%; silicon, not over 1.50% depending on the section of rail used and the intended C. .Preferably the reduction in area remaining to be suflicient to olgain an accurate section of the rail.

- The cooled rail is then reheated to a uniform temperature approximating 8009 C. and thereafter rolled to the desired finished size. The finished rails are thereafter allowed to cool to an average temperature of not less than 300 C. and are again reheated .to a uniform temperature approximating 800 G., and from this temperature are quenched, preferably in oil, until the surface temperature thereof approximates but is not less than about 250 C. The surface temperature of the rail should be carried to below the blue-heat temperature range. 'The quenched rails are then run into a furnace and heated to a uniform temperature above 300 C. but below the thermal critical range (approximating 600 (3.), for a predetermined time interval, approximating from 1 to 2 hours, following whichthey are allowed to cool slowly in the air to atmospheric temperatures. The exact annealing temperature and the time interval of annealing may be widely varied depending upon the composition of the steel, the degree of surface hardness desired, and upon the type of internal structure desired in the rail.

The rail product thus produced will be found to have retained the fine grained interior structure of my prior-patent with an exterior surface of greater hardness than heretofore obtainable by cold working means alone. For example, the finished rail product of my prior patent will have a surface A hardness of approximately 250-280, as measured on the Brinell scale. The finished rail product of the specific embodiment of the present invention will have a surface hardness approximating from 310 to 360, depending on the section and intended service of the heat treated rails.

A comparison of the other physical characteristics of the two types ,of rails are ap proximately as follows:

The rail product of my patent will produce rails having an elastic limit of from 70,000 to 90,000 lbs., an ultimate strength of from 130,000 to 150,000 lbs., an elongation in 2 in. of from 7% to 10%, and a reduction in area of from 8% to Therails produced in accordance with' the present application will have an elastic limit of from 110,000 to 145,000 lbs., an ultimate strength of from 155,000 to 180,000 lbs., an elongation in 2 in. of from 8% to 18%, and a reduction in area of from 20% to depending on the particular adjustment that is made in the heat treatment process to suit the section and the intended service of the treated rail.

While I have disclosed as a specific embodiment the steps of rolling the rail to a size larger than the desired finished size, cooling to below and then reheating to above the thermal critical range, and then rolling to the desired finishedsize. I may omit this particular sequence of steps and roll the rail directly down to the desired finished size if desired. The rail thus prepared may be cooled to temperatures below the thermal critical range, but above 300 C., reheated to a temperature approximating but above and shapes to increase .the surface hardness thereof which comprises heating the rail to a temperature approximating but above the thermal critical range, quenching the rail until the surface thereof is at a temperature approximating but not less than 250 0., reheating the rail to a temperature higher than the quenching temperature but below the thermal critical temperature and thereafter slowly cooling to atmospheric temperature. l

' 2. The method of hardening the surface of steel rails and shapes having the approximate composition of carbon 40-85%, manganese .401.60%, phosphorus .08%, sulphur 08% and silicon 1.50% which comprises heating the rail to a temperature approximating but above the thermal critical range, quenching the rail until the surface temperature thereof approximates but is not less than 250 (1., annealing the rail at temperatures approximately 600 C. and thereafter slowly cooling to room temperatures.

3. The method of hardening the surface of steel rails and shapes having the approximate composition of carbon .40.85%, manganese .401.60%, phosphorus .08%, sulphur 08% and silicon 1.50% which comprises heating the rail to a temperature approximating 800 0., quenching the rail until the surface temperature thereof approximates but is not less than 250 C., anealing the rail for a predetermined time interval at temperatures approximating 600 C. and thereafter slowly cooling to room temperatures.

4. The method of hardening the surface of steel rails and shapes having the approximate composition of carbon 40-85%, manganese .401.60%, phosphorous 08%, sulphur 08% and silicon 1.50% which comprises heating the rail to a temperature approximating 800 0., quenching the rail in water until the surface temperature thereof approximates but is not less than 250 0., annealing the rail at temperatures approximating 600 C. for approximately 1-2 hrs., and thereafter slowly cooling the rail to room temperatures.

5. The method of forming steel rails and shapes which comprises heating the rail billet to temperatures above the thermal critical range, rolling to a size larger than the desired finished rail size, cooling to a temperature below the thermal critical range but above about 300 0., reheating to a temperature approximating but above the thermal critical range, rolling to the desired finished size, cooling to a temperature below the thermal critical range but above about 300 0., reheating to a temperature approximating but above the thermal critical range, quenching until the surface temperature of the rail lies within the blue-heat range but above about 250 0., reheating to temperature above 300 0. but belowthe thermal critical range and thereafter cooling slowly to room temperatures.

6. The method of forming steel rails and shapes comprised of steel having the approximate composition of carbon .40.85%, manganese 404.60%, phosphorous 08%, sulphur 08%, and silicon 1.50%, which comprises heating the rail billet to a temperature above the thermal critical range, rolling to a size larger than the desired finished size, cooling to a temperature lower than the thermal critical range but above about 300 0., reheating to a temperature approximating but above the thermal critical range, rolling to the desired finished size, again cooling to a temperature below the thermal critical range but above about 300 0., reheating to a temperature approximating but above the thermal critical range, quenching the rail until the surface temperature thereof is within the blue-heat range but above about 250 0., annealing the rail at tern eratures approximating 600 0. and therea er slowly cooling to atmospheric temperatures.

7. The method of forming steel rails and shapes comprised of steel having the approximate composition of carbon .40-.85%,-manganese .401.60%, phosphorus 08%, sulphur 08%, and silicon 1.50%, which comprises heating the rail billet to a temperature above the thermal critical range, rolling to a size larger than the desired finished size, cooling toa temperature lower than the thermal critical range but above about 300 0., reheating to atemperature approximating but above the thermal critical range, rolling to the desired finished size, again cooling to atemperature below the thermal critical range but above about 300 0., reheating to a temperature approximating but above the ther mal ---f critical range, quenching the rail until the surface temperature thereof is within the blue-heat range but above about 250 0., annealing the rail at temperatures approximating 600 0.for a predetermined time interval and thereafter slowly cooling to atmospheric temperatures.

8. The method of forming steel rails and shapes comprised of steel having the approximate composition of carbon .40-.85%, manganese .401.60%, phosphorus 08%, sul- W it phur 08%, and silicon 1.50%, which comprises heating the rail billet to a. temperature above the thennal critical'range, rolling to a size larger than the desired finished size, cooling to a temperature lower than the thermal critical range but above about 300 0., re heating to a temperature approximating but above the thermal critical range, rolling to the desired finished size, again cooling to a temperature below the thermal critical range but above about 300 0., reheating to a tern perature approximating but above the thermal critical range, quenching the rail until the surface temperature thereof is within the blue-heat range but aboveabout 250 0., annealing the rail at temperatures approximating 600 0. for approximately 1-2 hrs., and thereafter slowly cooling to atmospheric temperatures.

9. The method of forming steel rails and shapeswhich comprises heating a rail billet to temperatures above the thermal critical range, rolling the rail to the desired finished size, cooling the rail .to temperatures below the thermal critical range but above about 300 0., reheating the rail to temperatures approximating but above the thermal critical range, quenching-the rail until the surface temperature thereof approximates but is above 250 0., annealing to temperatures above about 300 0. but below the thermal critical range and thereafter cooling slowly to room temperatures.

10. The method of forming steel rails and shapes from a rail billet having a composition approximating carbon 40-85%, manganese .401.60%, phosphorus 08%, sulphur 08%, silicon 1.50%, which comprises heating the rail billet to temperatures above the thermal critical range, rolling the rail to the desired finished size, cooling the rail to temperatures below the thermal critical range but above about 300 0., reheating to temperatures approximating but above the thermal critical range, quenching the rail until the surface temperature thereof approximates but is above about 250 0., annealing the rail to temperatures above 300 0. but less than the thermal critical range and thereafter slowly cooling to atmospheric temperatures.

11. The method of forming steel rails and shapes from a. rail billet having acomposition approximating carbon .40.85%, manganese 404.60%, phosphorus 08%, sulphur 08%, silicon 1.50%, which-comprises heating the rail billet to temperatures above the thermal critical range, rolling the rail to the desired finishedsize, cooling the rail to temperatures below the thermal critical range but above about 300 0., reheating to tem-' peratures approximating but above the thermal critical range, quenching the rail until the surface temperature thereof approximates but is above about 250 0., annealing the rail to temperatures above 300 0. but less than the thermal critical range for a predetermined time interval and thereafter slowly cooling to atmospheric temperatures.

12. The method of forming steel rails and shapes from a rail billet having a composition approximating carbon .40.85%, manganese 404.60%, phosphorus 08%, sulphur 08%, silicon 1.50%, which comprises heating the rail billet to temperatures above the thermal critical range, rolling the rail to the desired finished size, cooling the rail to temperatures below the thermal critical range but above about 300 C., reheating to temperatures approximating but above the thermal critical range, quenching the rail until the surface temperature thereof approximates but is above about 250 (3., annealing the rail to temperatures above 300 C. but less than the thermal critical range for approximately 1-2 hrs., and thereafter slowly cooling to atmospheric temperatures.

In witness whereof, I have hereunto signed my name.

JOHN BRUNNER. 

